I believe that climate change is occurring--the reduction in the size of global ice caps is hard to ignore. I also believe that human activity is a contributing factor.

I am uncertain how much of the warming, however, is attributable to man and how much is attributable to factors out of our control. I do not support radical feel-good policies like a unilateral U.S. cap-and-trade mandate. Such policies would have little efect on the climate but could cripple economic growth with devastating results for people across the planet....

So Romney went from believing that humans contribute to global warming, though he was uncertain how much, to saying he didn't know what contributes to global warming.

Easy to see why some would argue that's a flip flop. In this case it's something of a slow-motion flip flop since Romney appeared in August to be shifting away from the position he stated in his book.

After Sen. James Inhofe (R-OK), a well-known skeptic of the notion that human activity is causing climate change, criticized the Republican presidential candidate as "mushy" on the environment, Romney said at a town-hall meeting:

"Do I think the world's getting hotter? Yeah, I don't know that but I think that it is," he said. "I don't know if it's mostly caused by humans."

"What I'm not willing to do is spend trillions of dollars on something I don't know the answer to."

So if this is a flip flop, it might better be described as a slow-motion one that's taken a few few months to pull off.

Whatever it is, it was another chance for Romney's rivals to tee off on him since he, once again, drew attention to his reputation as an ideological chameleon.

This is ridiculous. Governor Romney's view on climate change has not changed. He believes it's occurring, and that human activity contributes to it, but he doesn't know to what extent. He opposes cap and trade, and he refused to sign such a plan when he was governor. Maybe the bigger threat is all the hot air coming from career politicians who are desperate to hold on to power."